I tagged along with
Capt. Bill Pike on the SC42 test, and one detail that turned our heads—actually
helped to snap “em back during those WOT speed runs—is the somewhat
ungainly named Integrated Exhaust Hull Structure (IEHS). By its nature
IEHS almost disappears into the finished boat, but its effects are noticeable.

In the construction
photo (right) you can see traditional round exhaust pipes about to be
linked from the engine manifolds to decidedly nontraditional “dump
boxes” (1), which are bonded both to the hull and to molded-in ducts
that run back along the bilge to the aft “thrust slots” (2).
As the big MAN 730s spool up, the many thousand cubic feet of exhaust
not only exit those underwater slots quietly, and without a chance to
splash or smudge the transom, but also help lift the SC42 onto plane.
Then carefully calibrated wedges worked into the bottom just forward of
the slots induce a suction that relieves the diesels of backpressure,
accounting in part for the SC42’s sporty acceleration. Plus, at idle
speeds, water sitting in the dump boxes helps with muffling and also switches
the exit to the bypass pipe (3), which is sized fairly small so that the
gases being ejected at the waterline (4) are accelerated away from the
boat. To top it all off, the rugged and essentially simple system occupies
less than half the space of conventional pipes and mufflers, which on
the SC42 creates the space for two deep fishbox/lockers molded into the
cockpit sole.

It’s a sign of
Hinckley’s pursuit of better boatbuilding technology that it is one
of the early adopters of IEHS, but the engineering is not exclusive to
it or any company. George VonWidmann (www.vonwidmanndesigns.com)
has spent nearly 15 years developing IEHS, and he says that some major
boatbuilder contracts, as well as a new level of exhaust/hull integration,
are about to be made public. Look for the whole story in next month’s
PMY. —Ben Ellison